WO2016084639A1

WO2016084639A1 - Organic electroluminescent element and material for organic electroluminescent elements

Info

Publication number: WO2016084639A1
Application number: PCT/JP2015/082093
Authority: WO
Inventors: 山田　哲也; 昇関根; 貴宗服部; 麻由香蟇目
Original assignee: コニカミノルタ株式会社
Priority date: 2014-11-25
Filing date: 2015-11-16
Publication date: 2016-06-02
Also published as: JPWO2016084639A1

Abstract

An objective of the present invention is to provide an organic EL element which has high luminous efficiency and excellent durability. Another objective of the present invention is to provide a material for organic EL elements, which is applicable to the above-described organic EL element and is able to be used in combination with a blue light emitting dopant. An organic electroluminescent element according to the present invention comprises organic layers which are sandwiched between a positive electrode and a negative electrode and include at least a light emitting layer. This organic electroluminescent element is characterized in that at least one of the organic layers contains a compound that has a structure represented by general formula (I).

Description

ORGANIC ELECTROLUMINESCENT ELEMENT AND MATERIAL FOR ORGANIC ELECTROLUMINESCENT ELEMENT

The present invention relates to an organic electroluminescence element and a material for an organic electroluminescence element. More specifically, the present invention relates to an organic electroluminescence element having high light emission efficiency and excellent durability and an organic electroluminescence element material used for the organic electroluminescence element.

An organic electroluminescence element (hereinafter also referred to as “organic EL element”) is an all-film thin film type composed of an organic thin film layer (single layer portion or multilayer portion) containing an organic light-emitting substance between an anode and a cathode. It is a solid element. When a voltage is applied to such an organic EL element, electrons are injected from the cathode into the organic thin film layer and holes are injected from the anode, and these are recombined in the light emitting layer (organic light emitting substance-containing layer) to generate excitons. The organic EL element is a light-emitting element using light emission (fluorescence / phosphorescence) from these excitons, and is a technology expected as a next-generation flat display and illumination.

Furthermore, since an organic EL element using phosphorescence emission from an excited triplet, which can realize a luminous efficiency of about 4 times in principle in comparison with an organic EL element using fluorescence emission, has been reported from Princeton University, Starting with the development of materials that exhibit phosphorescence at room temperature, research and development of light-emitting element layer configurations and electrodes are being carried out around the world.
As described above, the phosphorescence emission method is a method having a very high potential. However, in an organic EL device using phosphorescence emission, a method for controlling the position of the emission center is significantly different from that using fluorescence emission. How to recombine within the light emitting layer to stabilize the light emission is an important technical issue for capturing the efficiency and lifetime of the device.

Therefore, in recent years, multilayer stacked devices having a hole transport layer located on the anode side of the light emitting layer and an electron transport layer located on the cathode side of the light emitting layer in a form adjacent to the light emitting layer are well known. Yes. In addition, a mixed layer using a phosphorescent compound as a light emitting dopant and a host compound is often used for the light emitting layer.
On the other hand, from the viewpoint of materials, there is a great expectation for creating new materials for improving device performance. In particular, when utilizing blue phosphorescence, the blue phosphorescent compound itself has high triplet excited state (T ₁ ) energy (hereinafter also referred to as “T ₁ energy”). There is a strong demand for the development of peripheral materials having triplet excitation energy sufficiently higher than that of blue phosphorescent compounds.

As a peripheral material having high T ₁ energy, for example, a pyrazole derivative or imidazole is cyclized and trimerized, and a compound in which three pyrazole rings or imidazole rings are condensed to a triazine ring, ie, an organic compound using pyrazole trimer or imidazole trimer. Materials for EL devices have also been reported (see, for example, Patent Documents 1 to 3).

The pyrazole trimer and imidazole trimer described in the above documents have high T ₁ energy, but their use as a peripheral material for blue phosphorescent light emitting materials has not yet been reported.
For example, Patent Document 1 discloses an example in which a pyrazole trimer is applied to a host material of a phosphorescent dopant that emits green light, but there is no description used in combination with a blue light emitting dopant. This is presumed to be because, when pyrazole trimer is used as a material for an organic EL device, when it is laminated as a thin film, the inherent high T ₁ energy cannot be exhibited due to its associated state.

JP 2007-81050 A Japanese Patent Laying-Open No. 2005-082644 JP 2010-199592 A

The present invention has been made in view of the above-described problems and situations, and a problem to be solved is to provide an organic EL element having high luminous efficiency and excellent durability. Moreover, it is providing the organic EL element material which can be used in combination with the blue light emission dopant applicable to the said organic EL element.

As a result of examining the cause of the above-mentioned problem in order to solve the above-mentioned problems, the present inventor retains high T ₁ energy even in a thin film state and can be applied as a peripheral material of a blue light-emitting dopant. As a result, the present invention has been achieved.
That is, the said subject of this invention is solved by the following means.

1. An organic electroluminescence device having an organic layer including at least a light emitting layer sandwiched between an anode and a cathode,
At least 1 layer of the said organic layer contains the compound which has a structure represented by the following general formula (I), The organic electroluminescent element characterized by the above-mentioned.

(In the general formula (I), R ₁ to R ₆ each independently represents a hydrogen atom or an unsubstituted or substituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, amino group, Alkoxy group, aryloxy group, heterocyclic oxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group Alkylthio group, arylthio group, heterocyclic thio group, sulfonyl group, sulfinyl group, ureido group, phosphoramido group, hydroxy group, mercapto group, halogeno group, cyano group, sulfo group, carboxy group, nitro group, sulfino group, Hydrazino group, imi Group, a heteroaryl group, a silyl group or a silyloxy group. _However, if the substituent represented by R 1, _{R 3} and _{R 5} are all _identical, are at least one of R 2, _{R 4} and _{R 6} When at least one of R ₁ , R ₃ and R ₅ represents a different substituent, all the substituents represented by R ₂ , R ₄ and R ₆ may be the same.)

2. In the general formula (I), one to three of R ₁ to R ₆ are an aryl group or a heteroaryl group which are unsubstituted or have a substituent. Luminescence element.

3. 3. The organic electroluminescence device according to item 1 or 2, wherein in general formula (I), at least one of R ₁ to R ₆ is a heteroaryl group having a nitrogen atom.

4. The organic light-emitting device according to any one of claims 1 to 3, wherein the light-emitting layer contains a compound having a structure represented by the general formula (I).

5. An organic electroluminescent element material comprising a compound having a structure represented by the general formula (I) according to any one of items 1 to 4.

The above-described means of the present invention can provide an organic EL element having high luminous efficiency and excellent durability. Moreover, the organic EL element material which can be used in combination with the blue light emission dopant applicable to the said organic EL element can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
In general, it is known that it is desirable to reduce the π conjugate plane in order to increase the T ₁ energy. However, a compound having a small π-conjugated plane, that is, a monocyclic aromatic compound is not suitable for use as a material for an organic EL device because its molecular weight is low and thermal stability is low and sublimation is impossible. .

In contrast, pyrazole trimers and imidazole trimers have higher molecular weight and higher thermal stability than monocyclic aromatic compounds, and also have a particularly high T ₁ energy. Although it is an interesting structure as a material for an EL element, use of a blue phosphorescent material as a peripheral material has not been reported yet.
This is presumed to be because, when pyrazole trimer is used as a material for an organic EL element, when it is laminated as a thin film, the original high T ₁ energy cannot be exhibited.
This may be because some pyrazole trimers in the thin film are aggregated or crystallized due to the high planarity of the structure, thereby changing to a low T ₁ energy component. It is done.

Therefore, a compound having a structure represented by the general formula (I) according to the present invention in which substituents are arranged asymmetrically (hereinafter, also referred to as pyrazole trimer) reduces the cohesiveness between molecules, and allows crystals. The idea that it is suitable for the combination with a blue light-emitting dopant in that it is considered to have low properties. By preventing the aggregation and crystallization of the compound, the probability of occurrence of defects that cause reduction in luminous efficiency and lifetime, such as generation of low T ₁ energy components caused by these, and generation of trap sites for carrier movement It is guessed that can lower.

Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram of display part A Schematic diagram of pixels Schematic diagram of passive matrix type full color display device Schematic of lighting device Schematic diagram of lighting device Schematic configuration diagram of organic EL full-color display device Schematic configuration diagram of organic EL full-color display device Schematic configuration diagram of organic EL full-color display device Schematic configuration diagram of organic EL full-color display device Schematic configuration diagram of organic EL full-color display device

The organic EL device of the present invention is an organic electroluminescence device having an organic layer including at least a light emitting layer sandwiched between an anode and a cathode, wherein at least one of the organic layers is represented by the general formula (I). It contains a compound having the following structure.
This feature is a technical feature common to or corresponding to the claimed invention. The “pyrazole trimer” described in the present invention represents a structure in which three pyrazole rings are condensed to a hexahydrotriazine ring, which is the central skeleton of the general formula (I).

As an embodiment of the present invention, in General Formula (I), one to three of R ₁ to R ₆ are preferably unsubstituted or substituted aryl groups or heteroaryl groups. Thereby, the entropy at the time of forming a thin film increases from a viewpoint of steric hindrance, and a stable film can be obtained.

As an embodiment of the present invention, from the viewpoint of manifesting the effect of the present invention, in the general formula (I), at least one of R ₁ to R ₆ is preferably a heteroaryl group having a nitrogen atom. .

As an embodiment of the present invention, it is preferable that the light-emitting layer contains a compound having a structure represented by the general formula (I), so that the light emission efficiency can be improved.

The compound having the structure represented by the general formula (I) according to the present invention can be contained in a material for an organic electroluminescence device. Thereby, it can be used in combination with a blue light emitting dopant.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the following description, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

<< Constituent layers of organic EL elements >>
As typical element structures in the organic EL element of the present invention, the following structures can be exemplified, but the invention is not limited thereto.
(1) Anode / light emitting layer / cathode (2) Anode / light emitting layer / electron transport layer / cathode (3) Anode / hole transport layer / light emitting layer / cathode (4) Anode / hole transport layer / light emitting layer / electron Transport layer / cathode (5) anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (6) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode ( 7) Anode / hole injection layer / hole transport layer / (electron blocking layer /) light emitting layer / (hole blocking layer /) electron transport layer / electron injection layer / cathode

Among the above, the configuration (7) is preferably used, but is not limited thereto.
The light emitting layer according to the present invention is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the light emitting layers.
If necessary, a hole blocking layer (also referred to as a hole blocking layer) or an electron injection layer (also referred to as a cathode buffer layer) may be provided between the light emitting layer and the cathode. An electron blocking layer (also referred to as an electron barrier layer) or a hole injection layer (also referred to as an anode buffer layer) may be provided therebetween.

The electron transport layer according to the present invention is a layer having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer, and may be composed of a plurality of layers.
The hole transport layer according to the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer, and are composed of a plurality of layers. Also good.
In the above-described typical element configuration, a layer excluding the anode and the cathode is referred to as an “organic layer”.

(Tandem structure)
The organic EL element of the present invention may be a so-called tandem structure element in which a plurality of light emitting units including at least one light emitting layer are stacked.
As typical element configurations of the tandem structure, for example, the following configurations can be given.
Anode / first light emitting unit / intermediate layer / second light emitting unit / intermediate layer / third light emitting unit / cathode Here, the plurality of light emitting units may all be the same or different. Two light emitting units may be the same, and the remaining one may be different. The plurality of light emitting units may be laminated directly or via an intermediate layer (also referred to as an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, or an intermediate insulating layer), A known material structure can be used as long as it has a function of supplying electrons to the anode-side adjacent layer and holes to the cathode-side adjacent layer.

Examples of materials used for the intermediate layer include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiOx, VOx, CuI, InN, GaN, and CuAlO _2. , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ , Al and other conductive inorganic compound layers, two-layer films and multilayer films of these conductive inorganic compounds, fullerenes such as C ₆₀ , and conductive such as oligothiophene Examples include conductive organic compound layers, conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, and porphyrins, but the present invention is not limited thereto.
Preferred examples of the structure within the light emitting unit include those obtained by removing the anode and the cathode from the structures (1) to (7) mentioned in the above representative element structures, but the present invention is not limited to these. Not.

Specific examples of the tandem organic EL element include, for example, US Pat. No. 7,420,203, US Pat. No. 7,473,923, US Pat. No. 6,872,472, US Pat. No. 6,107,734, US Pat. No. 6,337,492. Description, Japanese Patent Application Laid-Open No. 2011-96679, Japanese Patent Application Laid-Open No. 2010-192719, Japanese Patent Application Laid-Open No. 2009-076929, Japanese Patent Application Laid-Open No. 2008-078414, Japanese Patent Application Laid-Open No. 2007-059848, International Publication No. 2005/094130. However, the present invention is not limited to these.
Hereinafter, each layer which comprises the organic EL element of this invention is demonstrated.

<Light emitting layer>
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode or the electron transport layer and the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer.
The total thickness of the light-emitting layers is not particularly limited, but the uniformity of the films that make up the layers and the prevention of applying unnecessary high voltages during light emission, as well as improving the stability of the emission color against the drive current From this viewpoint, it is preferably adjusted to a range of 2 nm to 5 μm, more preferably adjusted to a range of 2 to 200 nm, and particularly preferably adjusted to a range of 5 to 100 nm.

For the production of the light-emitting layer, a light-emitting dopant or a host compound, which will be described later, is used. Or the like, the ink jet method, the printing method, the spray coating method, the curtain coating method, the LB method (Langmuir Brodgett method, etc.).
The light emitting layer of the organic EL device of the present invention preferably contains a light emitting dopant (phosphorescent dopant, fluorescent light emitting dopant, etc.) compound and a host compound.

(1) Host compound The compound having a structure represented by the following general formula (I) according to the present invention can be used as a material for an organic EL device, and is particularly preferably used as a host compound.

In the general formula (I), R ₁ to R ₆ are each independently a hydrogen atom or an unsubstituted or substituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, amino group, alkoxy group. Group, aryloxy group, heterocyclic oxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, Alkylthio group, arylthio group, heterocyclic thio group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, hydroxy group, mercapto group, halogeno group, cyano group, sulfo group, carboxyl group, nitro group, sulfino group, hydrazino Group, imi It represents group, a heteroaryl group, a silyl group or a silyloxy group. However, when all the substituents represented by R ₁ , R ₃ and R ₅ are the same, at least one of R ₂ , R ₄ and R ₆ is different. When at least one of R ₁ , R ₃ and R ₅ represents a different substituent, all the substituents represented by R ₂ , R ₄ and R ₆ may be the same. Examples of the substituent that R ₁ to R ₆ have include the same substituents as the substituents represented by R ₁ to R ₆ .

The reason why the compound is preferably used as a host compound will be described.
So far, compounds having a pyrazole trimer skeleton are known, and those having an aryl group or a heteroaryl group as a substituent are also disclosed. Moreover, the example which used these compounds as an organic EL element material is also reported. However, organic EL devices using a compound having a pyrazole trimer skeleton have problems in terms of durability such as heat resistance and device life.

This is thought to be due to the fact that pyrazole trimers synthesized so far tend to agglomerate due to stacking because of their high planarity, and that crystallization is likely to occur because of their high symmetry. Therefore, it is presumed that deterioration in the organic EL device was caused by a change in film physical properties derived from the planarity and symmetry of the pyrazole trimer, which caused problems of durability such as heat resistance and device life.

In particular, there was no example in which a pyrazole trimer derivative was used as a peripheral material of a blue phosphorescent compound. This is probably because no pyrazole trimer derivative having sufficiently higher triplet excitation energy than the blue phosphorescent compound has been found so far.
For example, a compound in which the pyrazole trimer has an aryl group or a heteroaryl group at the 3-position and 4-position of each pyrazole ring in which the pyrazole trimer has already been reported, the π plane of the pyrazole trimer becomes an aryl group or a heteroaryl group. It is thought that triplet excitation energy decreases due to expansion.

On the other hand, in the present invention, a substituent having a structure represented by the general formula (I) is appropriately used as a peripheral material of a blue phosphorescent compound that can be applied as a material for an organic EL device. The pyrazole trimer introduced in is used.
That is, in the compound having the structure represented by the general formula (I) according to the present invention, a hydrogen atom or an arbitrary substituent is introduced so as to be asymmetric with respect to the six substitutable positions of the pyrazole trimer. It is characteristic that it is a structure.
Here, asymmetric means that the 3-position of each pyrazole ring constituting the pyrazole trimer, that is, when all the substituents represented by R ₁ , R ₃ and R ₅ are the same, R ₂ , R ₄ and R ₆ When at least one of them is different and at least one of R ₁ , R ₃ and R ₅ represents a different substituent, all the substituents represented by R ₂ , R ₄ and R ₆ may be the same. It means that.

In an organic EL element, one of the causes that the light emitting property of the element decreases is a change in the organic thin film. As a factor, it is conceivable that the organic compound constituting the organic thin film gradually moves and aggregates or crystallizes as the voltage is applied and driven. In general, molecules having high symmetry tend to have high crystallinity, and it is considered that crystallization is likely to occur with a pyrazole trimer in which substituents are symmetrically introduced.
On the other hand, in the present invention, by using a pyrazole trimer in which substituents are introduced asymmetrically, stacking between pyrazole trimer molecules is inhibited, and aggregation and crystallization can be prevented and amorphousness can be maintained. It is done.

Further, the entropy of the pyrazole trimer molecule itself is increased by the asymmetric modification, and the entropy of the thin film itself is also increased by using this as an organic thin film. An increase in entropy means a decrease in free energy, leading to an improvement in the stability of the thin film. As a result, it is presumed that the heat resistance of the organic EL element is improved.
Further, it is considered that the use of an organic thin film having high amorphousness and high stability improves the transportability of carriers such as electrons and holes, and it is assumed that the organic EL element can be driven at a low voltage. A decrease in driving voltage leads to an improvement in light emission efficiency and a reduction in the burden on the element, and also contributes to an extension of the element life.

In addition, the HOMO level and LUMO level of the molecule are adjusted by appropriately introducing substituents at substitutable positions of each pyrazole ring. By combining aryl groups or heteroaryl groups having various levels with pyrazole trimers having unique HOMO and LUMO levels, it is possible to tune the level of the whole molecule flexibly. Become. As a result, it is possible to meet the requirements for the level of the peripheral layer and the like, and it is considered that the light emission property and the device life could be improved.

As an embodiment of the present invention, in General Formula (I), one to three of R ₁ to R ₆ are preferably unsubstituted or substituted aryl groups or heteroaryl groups. Thereby, the entropy at the time of forming a thin film increases from a viewpoint of steric hindrance, and a stable film can be obtained.
The substituent represented by R ₁ to R ₆ is preferably one having a T ₁ energy of 2.70 eV or more (460 nm or less). For example, when a phenyl group is used as R ₁ , a compound in which the bond between R ₁ and a pyrazole trimer is replaced with a hydrogen bond, that is, when the T ₁ energy of benzene is 2.70 eV or more, the substituent represented by R ₁ is It can be preferably used.
Furthermore, the substituents R 1 _~ R ₆ represent may have one to improve the glass transition temperature Tg of the compound having the structure represented by the general formula (I) having R 1 _~ R _6, or an appropriate molecular weight R _The compound having a structure represented by the general formula (I) having ₁ to R ₆ can be appropriately selected depending on the purpose, such as a compound that imparts sublimation property under reduced pressure.

Specific examples of R ₁ to R ₆ include a hydrogen atom, alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, amino group, alkoxy group, aryloxy group, heterocyclic oxy group, acyl group, alkoxycarbonyl Group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, heterocyclic thio group, sulfonyl group, sulfinyl group Ureido group, phosphoric acid amide group, hydroxy group, mercapto group, halogeno group, cyano group, sulfo group, carboxy group, nitro group, sulfino group, hydrazino group, imino group, heteroaryl group or silyl group, silyloxy group, etc. Show.

Here, the alkyl group includes linear, branched or cyclic, preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, still more preferably 1 to 10 carbon atoms. Methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-octyl, n-nonyl, n-decyl, n-dodecyl, n-octadecyl, n-hexadecyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl , Cyclooctyl, 2-ethylhexyl, 1-adamantyl and the like.
In addition, the alkoxy group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and still more preferably 1 to 10 carbon atoms. Examples thereof include methoxy, ethoxy, butoxy, 2-ethylhexyloxy and the like. Can be mentioned.
The aryloxy group preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, still more preferably 6 to 12 carbon atoms, such as phenyloxy, 1-naphthyloxy or 2-naphthyloxy. Is mentioned.
The heterocyclic oxy group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and still more preferably 1 to 12 carbon atoms, and examples thereof include pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy and the like. .

The acyl group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, still more preferably 1 to 12 carbon atoms, and examples thereof include acetyl, benzoyl, formyl, and pivaloyl.
The alkoxycarbonyl group preferably has 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, and still more preferably 2 to 12 carbon atoms. Examples thereof include methoxycarbonyl and ethoxycarbonyl.
The aryloxycarbonyl group preferably has 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, still more preferably 7 to 12 carbon atoms, and examples thereof include phenyloxycarbonyl.
The acyloxy group preferably has 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, still more preferably 2 to 10 carbon atoms, and examples thereof include acetoxy and benzoyloxy.
The acylamino group preferably has 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, still more preferably 2 to 10 carbon atoms, and examples thereof include acetylamino and benzoylamino.

The alkylthio group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and still more preferably 1 to 12 carbon atoms. Examples thereof include methylthio and ethylthio.
The arylthio group preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, still more preferably 6 to 12 carbon atoms, and examples thereof include phenylthio.
The heterocyclic thio group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and still more preferably 1 to 12 carbon atoms. For example, pyridylthio, 2-benzimidazolylthio, 2-benz Examples include oxazolylthio and 2-benzthiazolylthio.

The sulfonyl group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, still more preferably 1 to 12 carbon atoms, and examples thereof include mesyl, tosyl, trifluoromethanesulfonyl and the like.
The sulfinyl group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, still more preferably 1 to 12 carbon atoms, and examples thereof include methanesulfinyl and benzenesulfinyl.
The phosphoric acid amide group preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, still more preferably 1 to 12 carbon atoms, and examples thereof include diethyl phosphoric acid amide and phenyl phosphoric acid amide. It is done.

Examples of the halogeno group include a fluoro group, a chloro group, a bromo group, and an iodo group.
The silyl group preferably has 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, still more preferably 3 to 24 carbon atoms, and examples thereof include trimethylsilyl and triphenylsilyl.
The silyloxy group preferably has 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, still more preferably 3 to 24 carbon atoms, and examples thereof include trimethylsilyloxy and triphenylsilyloxy.

The combination of R ₁ to R ₆ is not particularly limited within the above range, but the number of aryl groups and heteroaryl groups is preferably 1 to 3. By doing so, the π plane of the pyrazole trimer can be prevented from being expanded to an aryl group or a heteroaryl group, and the triplet excitation energy can be kept high by preventing the expansion of the conjugated system. It can also be suitably used for optical materials. In this case, as other substituents, groups that do not extend the conjugated system, specifically, alkyl groups, alkoxy groups, aryloxy groups, heterocyclic oxy groups, alkylthio groups, arylthio groups, heterocyclic thio groups, halogeno groups, A cyano group, a nitro group, a silyl group, and a silyloxy group can be exemplified, and an alkyl group, an alkoxy group, a halogeno group, a cyano group, and a silyl group are preferable.

As the aryl group or heteroaryl group, for example, phenyl group, triphenylene group, fluorene group, pyrrolyl group, furanyl group, thienyl group, pyrazolyl group, imidazolyl group, 1,2,3-triazolyl group, 1,2,4-triazolyl Group, tetrazolyl group, oxazolyl group, isoxazolyl group, oxadiazolyl group, thiazolyl group, isothiazolyl group, thiadiazolyl group, carbazolyl group, dibenzofuranyl group, dibenzothiophenyl group.
R ₁ to R ₆ are more preferably a heteroaryl group. In the case where R ₁ to R ₆ are heteroaryl groups and a covalent bond can be formed between a heteroatom other than carbon constituting the ring and a pyrazole trimer, it is more preferable that they are bonded with a heteroatom. . For example, the carbazolyl group can be bonded by carbon atoms or nitrogen atoms from the 1st position to the 8th position, but those bonded by a nitrogen atom are more preferable. Specific examples include a carbazolyl group, a benzimidazolyl group, and a diphenyltriazolyl group bonded with a nitrogen atom.

By introducing these substituents at the appropriate positions of the pyrazole trimer, it is possible to simultaneously improve the stability of the thin film and improve the carrier transportability at the time of device fabrication, and to adjust the HOMO level and LUMO level of the molecule. An organic EL device having excellent performance can be obtained.
Moreover, the organic EL device material of the present invention can be used by mixing with a symmetrically substituted pyrazole trimer. In this case, since the number of components in the organic thin film increases, the entropy in the film increases, the film quality is stabilized, and the light emission lifetime of the device is expected to be extended.

Hereinafter, specific examples of the compound having a structure represented by the general formula (I) according to the present invention will be given, but the present invention is not limited thereto. In addition, about the compound shown below, it is also preferable to have a substituent further to such an extent that a function is not inhibited.

[Method for Synthesizing Compound Having Structure Represented by General Formula (I)]
(1.1) Synthesis Example of H-11 The compound having the structure represented by the general formula (I) is described in Chem. Heterocycl. Compd. 30, 540, 1994 and Chem. Heterocycl. Compd. 32, p. 789, 1996.
For example, H-11 was obtained by heating 2 equivalents of 3-phenyl-5-pyrazolone and 1 equivalent of 3-xylyl-5-pyrazolone in the presence of phosphorus oxychloride. The obtained compound was measured by ¹ H-NMR and mass spectrometry and identified as the target product.

(1.2) Synthesis Example of H-24 H-24 is obtained by brominating an intermediate obtained by heating 3-methyl-5-pyrazolone in the presence of phosphorus oxychloride, followed by 1 to the pyrazole trimer. An equivalent amount of phenylboronic acid, biphenylboronic acid, and carbazolylphenylboronic acid was obtained by sequentially performing Suzuki-Miyaura coupling using a palladium catalyst. The obtained compound was measured by ¹ H-NMR and mass spectrometry and identified as the target product.

A host compound (also referred to as a light-emitting host or a light-emitting host compound) that can be used in the present invention has a mass ratio in the layer of 20% or more among the compounds contained in the light-emitting layer, and a room temperature ( 25 ° C.) is defined as a compound having a phosphorescence quantum yield of phosphorescence of less than 0.1. The phosphorescence quantum yield is preferably less than 0.01. Moreover, it is preferable that the mass ratio in the layer is 20% or more among the compounds contained in a light emitting layer.

In the present invention, one or more kinds of conventionally known host compounds may be used in combination. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient. Moreover, it becomes possible to mix different light emission by using multiple types of iridium complexes and / or conventionally well-known compounds used as a phosphorescence dopant mentioned later, and can thereby obtain arbitrary luminescent colors.

As the known host compound that can be used in combination with the present invention, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of light from being long-wavelength, and has a high Tg (glass transition temperature) is preferable. .
The host compound used in the present invention may be a low molecular compound, a high molecular compound having a repeating unit, or a low molecular compound (polymerizable host compound) having a polymerizable group such as a vinyl group or an epoxy group. Of course, one or more of such compounds may be used.

Specific examples of known host compounds include compounds described in the following documents.
JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445 gazette, 2002-343568 gazette, 2002-141173 gazette, 2002-352957 gazette, 2002-203683 gazette, 2002-363227 gazette, 2002-231453 gazette, No. 003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-260861, No. 2002-280183, No. 2002-299060, No. 2002. -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

(2) Luminescent dopant A luminescent dopant (a luminescent dopant, a dopant compound, or simply referred to as a dopant) will be described.
As the luminescent dopant, a fluorescent luminescent dopant (also referred to as a fluorescent dopant, a fluorescent compound, or a fluorescent luminescent compound), a phosphorescent dopant (also referred to as a phosphorescent dopant, a phosphorescent compound, a phosphorescent compound, or the like). .) Can be used.

(2.1) Phosphorescent dopant A phosphorescent dopant is a compound in which light emission from an excited triplet is observed, specifically a compound that emits phosphorescence at room temperature (25 ° C.), and a phosphorescence quantum yield. Is defined as a compound of 0.01 or more at 25 ° C., but a preferable phosphorescence quantum yield is 0.1 or more.
The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant used in the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. Just do it.

There are two types of light emission of the phosphorescent dopant in principle. One is the recombination of carriers on the host compound to which carriers are transported to generate the excited state of the luminescent host compound, and this energy is used as the phosphorescent dopant. It is an energy transfer type in which light emission from a phosphorescent dopant is obtained by moving to. The other is a carrier trap type in which a phosphorescent dopant becomes a carrier trap, and carrier recombination occurs on the phosphorescent dopant, and light emission from the phosphorescent dopant is obtained. In any case, it is a condition that the excited state energy of the phosphorescent dopant is lower than the excited state energy of the host compound.

Hereinafter, the phosphorescent compound (phosphorescent dopant) represented by the general formula (DP) and used suitably in the present invention will be described.

In the formula, M represents Ir, Pt, Rh, Ru, Ag, Cu, or Os. A ₁ , A ₂ , B ₁ and B ₂ each represent a carbon atom or a nitrogen atom. Ring Z ₁ represents a 6-membered aromatic hydrocarbon ring or 5-membered or 6-membered aromatic heterocycle formed together with A ₁ and A ₂ . Ring Z ₂ represents a 5-membered or 6-membered aromatic heterocycle formed together with B ₁ and B ₂ . Ring Z ₁ and ring Z ₂ may have a substituent, and the substituents may be bonded to each other to form a condensed ring structure. Moreover, the substituent of each ligand may couple | bond together and the ligands may connect. L ′ represents a monoanionic bidentate ligand coordinated to M. m ′ represents an integer of 0 to 2. n ′ represents an integer of 1 to 3. m ′ + n ′ is 2 or 3. When m ′ and n ′ are 2 or more, the ligands represented by the ring Z ₁ and the ring Z ₂ and L ′ may be the same or different.

In the general formula (DP), M can include Ir, Pt, Rh, Ru, Ag, Cu or Os, more preferably Ir, Pt, Rh, Ru or Os, and Ir, Pt or Os. It is more preferable that
A ₁ , A ₂ , B ₁ and B ₂ each represent a carbon atom or a nitrogen atom, and ring Z ₁ is a 6-membered aromatic hydrocarbon ring formed together with A ₁ and A ₂ , or 5 or 6 Represents a membered aromatic heterocycle, and ring Z ₂ represents a 5-membered or 6-membered aromatic heterocycle formed together with B ₁ and B ₂ .

Ring Z ₂ is preferably a 5-membered aromatic heterocyclic ring, and at least one of B ₁ and B ₂ is preferably a nitrogen atom.
Ring Z ₁ and ring Z ₂ may have a substituent, and the substituent is preferably an aryl group, heteroaryl group, silyl group, or alkyl group, more preferably a phenyl group, a carbazolyl group, or a dibenzo group. A furanyl group, a dibenzothiophenyl group, a triphenylsilyl group, a methyl group, and an isopropyl group, more preferably a phenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, and a triphenylsilyl group. Moreover, the substituents of the ring Z ₁ and the ring Z ₂ may be further bonded to each other to form a condensed ring structure. Moreover, the substituent of each ligand may mutually couple | bond together and the ligands may connect.

L ′ represents a monoanionic bidentate ligand coordinated to M.
m ′ represents an integer of 0 to 2, n ′ represents an integer of 1 to 3, and m ′ + n ′ is 2 or 3.
When m ′ and n ′ are 2 or more, the ligands represented by ring Z ₁ and ring Z ₂ and L ′ may be the same or different.
The structure of the general formula (DP) is preferably represented by the following general formula (DP-1) or (DP-2).

In the general formula (DP-1), M, A ₁ , A ₂ , B ₁ , B ₂ , ring Z ₁ , L ′, m ′ and n ′ are M, A ₁ , A ₂ in the general formula (DP). , B ₁ , B ₂ , ring Z ₁ , L ′, m ′ and n ′.
B ₃ to B ₅ are an atomic group forming an aromatic heterocyclic ring, and represent a hydrogen atom or a carbon atom, nitrogen atom, oxygen atom or sulfur atom which may have a substituent. Examples of the substituent that B ₃ to B ₅ have include the same groups as the substituents that the ring Z ₁ and the ring Z ₂ have in General Formula (DP).

The aromatic heterocycle formed by B ₁ to B ₅ in the general formula (DP-1) is represented by any of the structures of the following general formulas (DP-1a), (DP-1b), and (DP-1c). And is more preferably represented by the structure of the general formula (DP-1c).

In general formulas (DP-1a), (DP-1b), and (DP-1c), * 1 represents a binding site with A _{2 in} general formula (DP-1), and * 2 represents a binding site with M. To express.
Rb ₃ to Rb ₅ represent a hydrogen atom or a substituent, and the substituent represented by Rb ₃ to Rb ₅ has the same meaning as the substituents of the ring Z ₁ and the ring Z ₂ in the general formula (DP). Groups.
B ₄ and B ₅ in the general formula (DP-1a) are a carbon atom or a nitrogen atom, and more preferably at least one is a carbon atom.
In the general formula (DP-1b), B ₃ to B ₅ are a carbon atom or a nitrogen atom, and more preferably at least one is a carbon atom.
B ₃ and B ₄ in the general formula (DP-1c) are a carbon atom or a nitrogen atom, more preferably at least one is a carbon atom, and the substituents represented by Rb ₃ and Rb ₄ are further bonded to each other. It is more preferable that a condensed ring structure is formed, and the newly formed condensed ring structure is preferably an aromatic ring, and includes a benzimidazole ring, an imidazopyridine ring, an imidazopyrazine ring, or a purine ring. Either is preferable. Rb ₅ is preferably an alkyl group or an aryl group, and more preferably a phenyl group.

In the general formula (DP-2), M, A ₁ , A ₂ , B ₁ , B ₂ , ring Z ₁ , L ′, m ′ and n ′ are M, A ₁ , A ₂ in the general formula (DP). , B ₁ , B ₂ , ring Z ₁ , L ′, m ′ and n ′.
Ring Z ₂ represents a 5-membered aromatic heterocycle formed together with B ₁ to B ₃ .
A ₃ and B ₃ represent a carbon atom or a nitrogen atom, L ″ represents a divalent linking group. Examples of the divalent linking group represented by L ″ include an alkylene group, an alkenylene group, an arylene group, And a heteroarylene group, a divalent heterocyclic group, —O—, —S—, or a linking group in which these are arbitrarily combined.
The general formula (DP-2) is preferably further represented by the general formula (DP-2a).

In the general formula (DP-2a), M, A ₁ , A ₂ , B ₁ , B ₂ , ring Z ₁ , ring Z ₂ , L ′, m ′ and n ′ are M in the general formula (DP-2). , A ₁ , A ₂ , B ₁ , B ₂ , ring Z ₁ , ring Z ₂ , L ′, m ′ and n ′.
L ″ ₁ and L ″ ₂ represent C—Rb ₆ or a nitrogen atom, and Rb ₆ represents a hydrogen atom or a substituent. When L ″ ₁ and L ″ ₂ are C—Rb ₆ , Rb ₆ may be bonded to each other to form a ring.
In the general formulas (DP), (DP-1), (DP-2), and (DP-2a), A ₂ is preferably a carbon atom, and A ₁ is preferably a carbon atom. More preferably, the ring Z ₁ is a substituted or unsubstituted benzene ring or pyridine ring, and more preferably a benzene ring.

(2.2) Fluorescent dopant Examples of fluorescent dopants include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, Examples include perylene dyes, stilbene dyes, polythiophene dyes, rare-earth complex phosphors, and compounds having high fluorescence quantum yields typified by laser dyes.

[Combination with conventionally known dopants]
In addition, the light emitting dopant used in the present invention may be used in combination of a plurality of types of compounds, a combination of phosphorescent dopants having different structures, or a combination of a phosphorescent dopant and a fluorescent dopant.
Specific examples of known phosphorescent dopants that can be used in the present invention include compounds described in the following documents.
Nature, 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. , 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. , 17, 1059 (2005), International Publication No. 2009/100991, International Publication No. 2008/101842, International Publication No. 2003/040257, US Patent Application Publication No. 2006/835469, US Patent Application Publication No. 2006. No. 0202194, U.S. Patent Application Publication No. 2007/0087321, U.S. Patent Application Publication No. 2005/0244673, Inorg. Chem. , 40, 1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chem. lnt. Ed. , 2006, 45, 7800, Appl. Phys. Lett. 86, 153505 (2005), Chem. Lett. , 34, 592 (2005), Chem. Commun. , 2906 (2005), Inorg. Chem. , 42, 1248 (2003), International Publication No. 2009/050290, International Publication No. 2002/015645, International Publication No. 2009/000673, US Patent Application Publication No. 2002/0034656, and US Pat. No. 7,332,232. United States Patent Application Publication No. 2009/0108737, United States Patent Application Publication No. 2009/0039776, United States Patent No. 6921915, United States Patent No. 6,687,266, United States Patent Application Publication No. 2007/0190359. No., US Patent Application Publication No. 2006/0008670, US Patent Application Publication No. 2009/0165846, US Patent Application Publication No. 2008/0015355, US Pat. No. 7,250,226, US Patent No. 7396598 Writing, U.S. Patent Application Publication No. 2006/0263635, U.S. Patent Application Publication No. 2003/0138657, U.S. Patent Application Publication No. 2003/0152802, U.S. Patent No. 7090928, Angew. Chem. lnt. Ed. 47, 1 (2008), Chem. Mater. , 18, 5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics, 23, 3745 (2004), Appl. Phys. Lett. , 74, 1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/009024, International Publication No. 2006/056418, International Publication No. 2005/019373, International Publication No. 2005/123873, International Publication. No. 2005/123873, International Publication No. 2007/004380, International Publication No. 2006/082742, US Patent Application Publication No. 2006/0251923, US Patent Application Publication No. 2005/0260441, US Pat. No. 7,393,599. No. 7, U.S. Pat. No. 7,534,505, U.S. Pat. No. 7,445,855, U.S. Patent Application Publication No. 2007/0190359, U.S. Patent Application Publication No. 2008/0297033, U.S. Pat. No. 7,338,722. Letter, United States Published Patent Application No. 2002/0134984, U.S. Pat. No. 7,279,704, U.S. Patent Application Publication No. 2006/098120, U.S. Patent Application Publication No. 2006/103874, International Publication No. 2005/076380. International Publication No. 2010/032663, International Publication No. 2008/140115, International Publication No. 2007/052431, International Publication No. 2011/134013, International Publication No. 2011/157339, International Publication No. 2010/086089, International Publication No. Publication No. 2009/113646, International Publication No. 2012/020327, International Publication No. 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149, US Patent Application Publication No. 2012/228583 , Rice Japanese Patent Application Publication No. 2012/212126, Japanese Patent Application Laid-Open No. 2012-069737, Japanese Patent Application Laid-Open No. 2011-181303, Japanese Patent Application Laid-Open No. 2009-114086, Japanese Patent Application Laid-Open No. 2003-81988, Japanese Patent Application Laid-Open No. 2002-302671. Japanese Patent Laid-Open No. 2002-363552.
Among these, a preferable phosphorescent dopant includes an organometallic complex having Ir as a central metal. More preferably, a complex containing at least one coordination mode among a metal-carbon bond, a metal-nitrogen bond, a metal-oxygen bond, and a metal-sulfur bond is preferable.
Here, although the specific example of the well-known phosphorescence dopant which can be used for this invention is given, this invention is not limited to these.

As a combination of the compound having the structure represented by the general formula (I) and the phosphorescent compound according to the present invention, a blue phosphorescent dopant can be particularly preferably used.
Particularly preferably used dopants include D-36, D-37, D-41, D-53, D-54, D-55, D-56, D-61, D-63, D-67, D- 80. In terms of achieving a deeper blue color, that is, a lower CIE y value, D-41, D-53, D-54, D-55, and D-56 are more preferable, achieving a longer life and higher durability. In view of this, D-36, D-37, and D-63 are more preferable.

《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided with a single layer or a plurality of layers.
The electron transport layer only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer, and as a constituent material of the electron transport layer, any one of conventionally known compounds may be selected and used in combination. Is also possible.

Examples of conventionally known materials used for the electron transport layer (hereinafter referred to as electron transport materials) include polycyclic aromatic hydrocarbons such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, Heterocyclic tetracarboxylic anhydride, carbodiimide, fluorenylidenemethane derivative, anthraquinodimethane and anthrone derivative, oxadiazole derivative, carboline derivative or at least one carbon atom of the hydrocarbon ring constituting the carboline ring of the carboline derivative And derivatives having a ring structure in which one is substituted with a nitrogen atom, hexaazatriphenylene derivatives and the like.
Furthermore, in the oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron-withdrawing group can also be used as an electron transport material.
It is also possible to use a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain.

In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga, or Pb can also be used as the electron transport material.
In addition, metal-free or metal phthalocyanine, or those having a terminal substituted with an alkyl group or a sulfonic acid group can be used as the electron transport material.
An inorganic semiconductor such as n-type-Si and n-type-SiC can also be used as an electron transport material.

The electron transport layer is made of, for example, a vacuum deposition method, a wet method (also referred to as a wet process, such as a spin coating method, a casting method, a die coating method, a blade coating method, a roll coating method, an inkjet method, a printing method, The film is preferably formed by thinning by a spray coating method, a curtain coating method, an LB method (such as Langmuir's Brodgett method)).

The thickness of the electron transport layer is not particularly limited, but is usually about 5 to 5000 nm, preferably 5 to 200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.
Further, an n-type dopant such as a metal compound such as a metal complex or a metal halide may be doped.

As an example of a conventionally known electron transport material preferably used for forming the electron transport layer of the organic EL device of the present invention, the compounds described in International Publication No. 2013/061850 can be preferably used. It is not limited to.

"cathode"
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.
In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the emission luminance is advantageously improved.
In addition, a transparent or semi-transparent cathode can be produced by producing a conductive transparent material, which will be described later in the description of the anode, after producing the above metal with a thickness of 1 to 20 nm on the cathode. By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

<< Injection layer: electron injection layer (cathode buffer layer), hole injection layer >>
The injection layer is provided as necessary, and there are an electron injection layer and a hole injection layer, and as described above, exists between the anode and the light emitting layer or the hole transport layer, and between the cathode and the light emitting layer or the electron transport layer. You may let them.
An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).

The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Representative phthalocyanine buffer layer, hexaazatriphenylene derivative buffer layer, oxide buffer layer typified by vanadium oxide, amorphous carbon as described in JP-T-2003-519432, JP-A-2006-135145, etc. Examples thereof include a buffer layer, a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) and polythiophene, and an orthometalated complex layer represented by tris (2-phenylpyridine) iridium complex.

The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by, alkali metal compound buffer layer typified by lithium fluoride and potassium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride and cesium fluoride, typified by aluminum oxide Examples thereof include an oxide buffer layer. The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm, although it depends on the material.

<Blocking layer: hole blocking layer, electron blocking layer>
As described above, the blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film. For example, it is described in JP-A Nos. 11-204258 and 11-204359, and “Organic EL elements and the forefront of industrialization (published by NTT Corporation on November 30, 1998)” on page 237. There is a hole blocking (hole blocking) layer.

The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material having a function of transporting electrons and a very small ability to transport holes. By blocking the holes, the probability of recombination of electrons and holes can be improved.
Moreover, the structure of the electron carrying layer mentioned above can be used as a hole-blocking layer as needed.
The hole blocking layer of the organic EL device of the present invention is preferably provided adjacent to the light emitting layer.
The hole blocking layer includes a carbazole derivative, a carboline derivative, a diazacarbazole derivative (the diazacarbazole derivative is a nitrogen atom in which any one of carbon atoms constituting the carboline ring is cited as the host compound described above. It is preferable to contain the thing replaced by.

On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material having a function of transporting holes while having a remarkably small ability to transport electrons. The probability of recombination of electrons and holes can be improved by blocking.
Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed. The thickness of the hole blocking layer and the electron transporting layer according to the present invention is preferably 3 to 100 nm, and more preferably 5 to 30 nm.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.
The hole transport material has any of hole injection or transport and electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers, particularly thiophene oligomers.
In addition, azatriphenylene derivatives such as those described in JP-T-2003-519432 and JP-A-2006-135145 can also be used as hole transport materials.

Although the above-mentioned thing can be used as a positive hole transport material, It is preferable to use a porphyrin compound, an aromatic tertiary amine compound, and a styryl amine compound, especially an aromatic tertiary amine compound.
Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ′, N′-tetraphenyl-4,4′-diaminophenyl; N, N′-diphenyl-N, N′— Bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' - (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbene; N-phenylcarbazole, and further two fused aromatic rings described in US Pat. No. 5,061,569. Those possessed in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), Japanese Patent Laid-Open No. 4-308688 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (MTDATA), etc., in which the triphenylamine units described in 3 are linked in a three star burst type Is mentioned.

Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.
In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material and the hole transport material.
JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material as described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, these materials are preferably used because a light-emitting element with higher efficiency can be obtained.

The hole transport layer is formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. Can do.
The layer thickness of the hole transport layer is not particularly limited, but is usually about 5 nm to 5 μm, preferably 5 to 200 nm. This hole transport layer may have a single layer structure composed of one or more of the above materials.

Alternatively, a hole transport layer having a high p property doped with impurities can be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.
In the present invention, it is preferable to use a hole transport layer having such a high p property because a device with lower power consumption can be produced.

"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such an electrode substance include metals such as Au, and conductive transparent materials such as CuI, ITO, SnO ₂ , and ZnO.
Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, a thin film may be formed by vapor deposition or sputtering of these electrode materials, and a pattern of a desired shape may be formed by photolithography, or when pattern accuracy is not required (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material.

Alternatively, when a material that can be applied, such as an organic conductive compound, is used, a wet film formation method such as a printing method or a coating method can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

《Support substrate》
The support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention is not particularly limited in the type of glass, plastic, etc., and is transparent. Or opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element.

Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate ( CAP), cellulose esters such as cellulose acetate phthalate, cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones Cycloolefin resins such as polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylates, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned.

The surface of the resin film may be formed with an inorganic film, an organic film, or a hybrid film of both, and the water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. Gas barrier film having a relative humidity (90 ± 2)%) of 0.01 g / m ² · 24 h or less, and oxygen permeability measured by a method in accordance with JIS K 7126-1987. However, it is preferably a high gas barrier film having 1 × 10 ⁻³ ml / m ² · 24 h · atm or less and a water vapor permeability of 1 × 10 ⁻⁵ g / m ² · 24 h or less.

The material for forming the gas barrier layer may be any material as long as it has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. . Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

The method for forming the gas barrier layer is not particularly limited. For example, the vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma weight A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, and the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.
Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films, opaque resin substrates, and ceramic substrates.

The external extraction yield at room temperature for light emission of the organic EL device of the present invention is preferably 1% or more, and more preferably 5% or more.
Here, the external extraction quantum yield (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons sent to the organic EL element × 100.
In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor may be used in combination. In the case of using a color conversion filter, the λmax of light emission of the organic EL element is preferably 480 nm or less.

<< Materials for organic EL elements >>
The material for an organic EL device of the present invention contains a compound having a structure represented by the general formula (I).
Since the compound having the structure represented by the general formula (I) is expected to function as a host compound, it is preferably used for the light emitting layer. In addition to the compound having the structure represented by the general formula (I), various functional materials may be contained.

<< Method for producing organic EL element >>
As an example of a method for producing an organic EL device, a device comprising an anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer (electron injection layer) / cathode Will be described.
First, a desired electrode material, for example, a thin film made of an anode material is formed on a suitable substrate so as to have a thickness of 1 μm or less, preferably 10 to 200 nm, to produce an anode.
Next, a thin film containing an organic compound such as a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, or a cathode buffer layer, which is an element material, is formed thereon.

As a method for forming a thin film, for example, a thin film can be formed by a vacuum deposition method, a wet method (also referred to as a wet process), or the like.
Wet methods include spin coating, casting, die coating, blade coating, roll coating, ink jet, printing, spray coating, curtain coating, and LB, but precise thin films can be formed. From the viewpoint of high productivity, a method having high suitability for the roll-to-roll method such as a die coating method, a roll coating method, an ink jet method, and a spray coating method is preferable. Different film formation methods may be applied for each layer.

Examples of the liquid medium for dissolving or dispersing the organic EL device material such as a light-emitting dopant used in the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, and halogenated hydrocarbons such as dichlorobenzene. , Aromatic hydrocarbons such as toluene, xylene, mesitylene, and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as dimethylformamide (DMF) and DMSO can be used.
Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.

After these layers are formed, a thin film made of a cathode material is formed thereon so as to have a thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a desired organic EL device can be obtained by providing a cathode. .
Further, the order can be reversed, and the cathode, cathode buffer layer, electron transport layer, hole blocking layer, light emitting layer, hole transport layer, hole injection layer, and anode can be formed in this order.
The organic EL device of the present invention is preferably produced from the hole injection layer to the cathode consistently by a single evacuation, but it may be taken out halfway and subjected to different film forming methods. At that time, it is preferable to perform the work in a dry inert gas atmosphere.

<Other configuration>
As a sealing means, a protective film, a protective plate, a technique for improving light extraction efficiency and a light collecting sheet that can be used in the present invention, a known technique described in JP 2014-152151 A can be used. .

<Application>
The organic EL element of the present invention can be used as an electronic device, a display device, a display, and various light emitting devices. Examples of light emitting devices include lighting devices (home lighting, interior lighting), clocks and backlights for liquid crystals, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, Especially, it can use effectively for the use as a backlight of a liquid crystal display device, and a light source for illumination.

In the organic EL device of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like during film formation, if necessary. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned. In the fabrication of the element, a conventionally known method is used. Can do.

The light emission color of the organic EL device of the present invention and the compound used in the present invention is shown in FIG. 7.16 on page 108 of “New Color Science Handbook” (edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with a luminance meter CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.
When the organic EL element of the present invention is a white element, white means that the chromaticity in the CIE1931 color system at 1000 cd / m ² is X when the 2 ° viewing angle front luminance is measured by the above method. = 0.33 ± 0.07 and Y = 0.33 ± 0.1.

<Display device>
The organic EL element of the present invention can be used for a display device. The display device may be single color or multicolor, but here, the multicolor display device will be described.
In the case of a multicolor display device, a shadow mask is provided only at the time of forming a light emitting layer, and a film can be formed on one surface by vapor deposition, casting, spin coating, ink jet, printing, or the like.
In the case of patterning only the light emitting layer, the method is not limited. However, the vapor deposition method, the ink jet method, the spin coating method, and the printing method are preferable.

The configuration of the organic EL element provided in the display device is selected from the above-described configuration examples of the organic EL element as necessary.
Moreover, the manufacturing method of an organic EL element is as having shown to the one aspect | mode of manufacture of the organic EL element of said invention.
When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.

The multicolor display device can be used as a display device, a display, and various light emission sources. In a display device or display, full-color display is possible by using three types of organic EL elements of blue, red, and green light emission.
Examples of the display device and display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in an automobile. In particular, it may be used as a display device for reproducing still images and moving images, and the driving method when used as a display device for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.
Light emitting sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. However, the present invention is not limited to these.

Hereinafter, an example of a display device having the organic EL element of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an example of a display device composed of organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element.
The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, a wiring unit C that electrically connects the display unit A and the control unit B, and the like. .
The control unit B is electrically connected to the display unit A via the wiring unit C, and sends a scanning signal and an image data signal to each of a plurality of pixels based on image information from the outside. Sequentially emit light according to the image data signal, scan the image, and display the image information on the display unit A.

FIG. 2 is a schematic diagram of a display device using an active matrix method.
The display unit A includes a wiring unit C including a plurality of scanning lines 5 and data lines 6, a plurality of pixels 3 and the like on a substrate. The main members of the display unit A will be described below.
FIG. 2 shows a case where the light emitted from the pixel 3 (the emitted light L) is extracted in the white arrow direction (downward).

The scanning lines 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a lattice shape and are connected to the pixels 3 at the orthogonal positions (details are shown in FIG. Not shown).
When a scanning signal is applied from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data.
Full-color display is possible by appropriately arranging pixels in the red region, the green region, and the blue region on the same substrate.

Next, the light emission process of the pixel will be described. FIG. 3 is a schematic diagram showing a pixel circuit.
The pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. A full color display can be performed by using red, green, and blue light emitting organic EL elements as the organic EL elements 10 in a plurality of pixels, and juxtaposing them on the same substrate.

3, an image data signal is applied from the control unit B to the drain of the switching transistor 11 via the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is supplied to the capacitor 13 and the driving transistor 12. Is transmitted to the gate.

By transmitting the image data signal, the capacitor 13 is charged according to the potential of the image data signal, and the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10, and the power supply line 7 connects to the organic EL element 10 according to the potential of the image data signal applied to the gate. Current is supplied.

When the scanning signal is moved to the next scanning line 5 by the sequential scanning of the control unit B, the driving of the switching transistor 11 is turned off. However, since the capacitor 13 holds the charged potential of the image data signal even if the driving of the switching transistor 11 is turned off, the driving of the driving transistor 12 is kept on and the next scanning signal is applied. Until then, the light emission of the organic EL element 10 continues. When the scanning signal is next applied by sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.
That is, the organic EL element 10 emits light by the switching transistor 11 and the drive transistor 12 that are active elements for the organic EL element 10 of each of the plurality of pixels, and the light emission of the organic EL element 10 of each of the plurality of pixels 3. It is carried out. Such a light emitting method is called an active matrix method.

Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or by turning on / off a predetermined light emission amount by a binary image data signal. Good. The potential of the capacitor 13 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.
In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

FIG. 4 is a schematic view of a passive matrix display device. In FIG. 4, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice shape so as to face each other with the pixel 3 interposed therebetween.
When the scanning signal of the scanning line 5 is applied by sequential scanning, the pixels 3 connected to the applied scanning line 5 emit light according to the image data signal.
In the passive matrix system, the pixel 3 has no active element, and the manufacturing cost can be reduced.
By using the organic EL element of the present invention, a display device with improved luminous efficiency was obtained.

《Lighting device》
The organic EL element of the present invention can also be used for a lighting device.
The organic EL element of the present invention may be used as an organic EL element having a resonator structure. Examples of the purpose of use of the organic EL element having such a resonator structure include a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processing machine, and a light source of an optical sensor. It is not limited. Moreover, you may use for the said use by making a laser oscillation.
Further, the organic EL element of the present invention may be used as a kind of lamp for illumination or exposure light source, a projection device for projecting an image, or a type for directly viewing a still image or a moving image. It may be used as a display device (display).
The driving method when used as a display device for reproducing a moving image may be either a passive matrix method or an active matrix method. Alternatively, a full-color display device can be manufactured by using two or more organic EL elements of the present invention having different emission colors.

Further, the compound having the structure represented by the general formula (I) according to the present invention can be applied to an organic EL element that emits substantially white light as a lighting device. For example, when a plurality of light emitting materials are used, white light emission can be obtained by simultaneously emitting a plurality of light emission colors and mixing the colors. As a combination of a plurality of light emission colors, the light emission may include three light emission maximum wavelengths of three primary colors of red, green and blue, or two light emission utilizing a complementary color relationship such as blue and yellow, blue green and orange, etc. It may contain a maximum wavelength.

In addition, the method for forming the organic EL device of the present invention may be simply arranged by providing a mask only when forming a light emitting layer, a hole transport layer, an electron transport layer, or the like, and separately coating with the mask. Since the other layers are common, patterning of a mask or the like is unnecessary, and for example, an electrode film can be formed on one surface by a vapor deposition method, a cast method, a spin coating method, an ink jet method, a printing method, or the like, and productivity is improved.
According to this method, unlike a white organic EL device in which light emitting elements of a plurality of colors are arranged in parallel in an array, the elements themselves are luminescent white.

[One aspect of lighting device]
One mode of a lighting device including the organic EL element of the present invention will be described.
The non-light emitting surface of the organic EL device of the present invention is covered with a glass case, a 300 μm thick glass substrate is used as a sealing substrate, and an epoxy photocurable adhesive (LUX The track LC0629B) is applied, and this is overlaid on the cathode and brought into close contact with the transparent support substrate, irradiated with UV light from the glass substrate side, cured, sealed, and illuminated as shown in FIGS. A device can be formed.

FIG. 5 shows a schematic diagram of the lighting device, and the organic EL element of the present invention (organic EL element 101 in the lighting device) is covered with a glass cover 102 (note that the sealing operation with the glass cover is performed by lighting. This was performed in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) without bringing the organic EL element 101 in the apparatus into contact with the air.
FIG. 6 is a cross-sectional view of the lighting device. In FIG. 6, reference numeral 105 denotes a cathode, 106 denotes an organic layer, and 107 denotes a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.
By using the organic EL element of the present invention, an illumination device with improved luminous efficiency was obtained.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in an Example, unless otherwise indicated, "volume%" is represented.

[Example 1]
<< Production of organic EL element >>
(1) Production of Organic EL Element 1-1 After forming a film of ITO (indium tin oxide) with a thickness of 150 nm on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm and performing patterning, The transparent substrate with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
Further, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (abbreviated as PEDOT / PSS, manufactured by Bayer, Baytron P Al 4083) with pure water was formed on this substrate by spin coating. Then, it dried at 140 degreeC for 1 hour, and provided the positive hole injection layer with a layer thickness of 50 nm. This transparent substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

After depressurizing to a vacuum of 1 × 10 ⁻⁴ Pa, the deposition crucible containing compound HT-1 was energized and heated, deposited on the hole injection layer at a deposition rate of 0.1 nm / second, and a layer thickness of 10 nm. The hole transport layer was formed.
Next, the comparative compound (1) as the host compound and D-63 as the phosphorescent compound were co-deposited at a deposition rate of 0.1 nm / second so that the volume percentage was 94% and 6%, respectively, and the layer thickness was 30 nm. A light emitting layer was formed.

Next, compound HB-1 was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 5 nm, and subsequently compound Alq (tris (8-hydroxyquinolinato) aluminum) was deposited at a deposition rate of 0.1 nm / second. Vapor deposition was performed in seconds to form an electron transport layer having a layer thickness of 30 nm. Furthermore, after forming potassium fluoride with a film thickness of 2 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
A can-shaped glass cover was adhered to the non-light-emitting surface side of the above element using a UV curable resin in a nitrogen atmosphere to prepare an organic EL element 1-1.
In addition, the compound used in a present Example has the following chemical structural formula.

(2) Preparation of Organic EL Elements 1-2 to 1-7 Organic EL Element 1 except that Comparative Compound (1) as a host compound was changed to the compounds shown in Table 1 in the preparation of Organic EL element 1-1. Organic EL elements 1-2 to 1-7 were produced in the same manner as in the production of -1.

<< Evaluation of Organic EL Elements 1-1 to 1-7 >>
The following evaluation was performed for each organic EL element. The evaluation results are shown in Table 1.
(1) Luminous efficiency (EQE, external extraction quantum efficiency)
The organic EL device was energized under a constant current condition of room temperature (25 ° C.) and 2.5 mA / cm ² , and the light emission luminance (L ₀ ) [cd / m ² ] immediately after the start of light emission was measured. The quantum efficiency (η) was calculated.
Here, the measurement of emission luminance was performed using CS-2000 (manufactured by Konica Minolta), and the external extraction quantum efficiency was expressed as a relative value with the organic EL element 1-2 being 100.
A larger value indicates higher efficiency for comparison.

(2) Half-life The half-life was evaluated according to the measurement method shown below.
Each organic EL element was driven at a constant current with a current giving an initial luminance of 4000 cd / m ² , and a time during which the initial luminance was ½ was obtained. The half life was expressed as a relative value with the organic EL element 1-2 being 100.
In addition, the one where a value is large shows that durability is excellent with respect to the comparison.

(3) Driving voltage The driving voltage was measured when the organic EL element was energized under a constant current condition of room temperature (25 ° C.) and 2.5 mA / cm ^2. Expressed by value.
Note that a smaller value indicates that the driving voltage is lower than the comparison, and the luminous efficiency is excellent.

(4) Storage stability (heat resistance)
The organic EL elements 1-1 to 1-7 were energized under a constant current condition of ^2.5 mA / cm ² , measured for emission spectrum and emission chromaticity (CIE color system), and then in a constant temperature bath at 60 ° C. Stored for 12 hours.
After storage and cooling to room temperature, the spectrum and emission chromaticity were measured under constant current conditions of ^2.5 mA / cm ² . The distance between the CIE chromaticity coordinates, x, y coordinates before storage and the x ′, y ′ coordinates after storage is evaluated, and the relative value with the distance of the organic EL element 1-2 as 100 is obtained. It was shown in 1. Smaller numbers indicate better storage. In addition, when the height of the light emission maximum value (λmax) after storage was less than 60% before storage, it was shown as x in Table 1 because it was particularly inferior.

As described above, when the compound having the structure represented by the general formula (I) according to the present invention is used as the host compound with respect to the comparative compounds (1) to (3), the emission voltage is high, the lifetime is long, and the driving voltage is high. It was low and excellent in heat resistance, and it was found that the organic EL device using the compound having the structure represented by the general formula (I) according to the present invention has both high luminous efficiency and durability.

[Example 2]
<< Production of organic EL element >>
(1) Preparation of organic EL element 2-1 In the preparation of organic EL element 1-1, the organic EL element was changed except that the host compound was changed to comparative compound (2) and the phosphorescent compound was changed to D-41. Organic EL element 2-1 was produced in the same manner as in 1-1.
(2) Preparation of organic EL elements 2-2 to 2-7 In the preparation of organic EL element 2-1, organic EL element 2 was used except that comparative compound (2) as a host compound was changed to the compounds shown in Table 2. Organic EL elements 2-2 to 2-7 were produced in the same manner as in the production of -1.

<< Evaluation of organic EL elements 2-1 to 2-7 >>
Evaluation similar to Example 1 was performed about each organic EL element. The evaluation results are shown in Table 2 as relative values with the organic EL element 2-1 being 100.

As described above, even when D-41 is used as the phosphorescent compound, the compound having the structure represented by the general formula (I) according to the present invention is used as the host for the comparative compounds (2) and (3). When used as a compound, an organic EL device using a compound having a high light emission efficiency, a long lifetime, a low driving voltage, excellent heat resistance, and having a structure represented by the general formula (I) according to the present invention. It was found that both high luminous efficiency and durability were achieved.

Example 3
<< Production of organic EL element >>
(1) Preparation of organic EL element 3-1 In the preparation of organic EL element 1-1, in the formation of the light emitting layer, comparative compound (2) as the host compound and D-54 as the phosphorescent compound were each 90%, A light emitting layer of 30 nm is formed so as to be 10% by volume. Further, in the formation of the hole blocking layer, the hole blocking material is changed from HB-1 to BAlq (bis (2-methyl-8-quinolinolato) (4- An organic EL element 3-1 was produced in the same manner as in the production of the organic EL element 1-1 except that (phenylphenolato) aluminum (III)) was changed.

(2) Preparation of organic EL elements 3-2 to 3-6 Organic EL element 3 except that comparative compound (2) as a host compound was changed to the compounds shown in Table 3 in the preparation of organic EL element 3-1. Organic EL elements 3-2 to 3-6 were produced in the same manner as in the production of -1.

<< Evaluation of organic EL elements 3-1 to 3-6 >>
Evaluation similar to Example 1 was performed about each organic EL element. The evaluation results are shown in Table 3 in terms of relative values where the organic EL element 3-2 is 100.

As described above, even when D-54 is used as the phosphorescent compound, the compound having the structure represented by the general formula (I) according to the present invention is used as the host for the comparative compounds (2) and (3). When used as a compound, an organic EL device using a compound having a high light emission efficiency, a long lifetime, a low driving voltage, excellent heat resistance, and having a structure represented by the general formula (I) according to the present invention. It was found that both high luminous efficiency and durability were achieved.

Example 4
<< Production of organic EL element >>
(1) Preparation of organic EL element 4-1 In the preparation of organic EL element 3-1, the host compound was changed to comparative compound (1), and the phosphorescent compound was changed to D-20. Organic EL element 4- 1 was produced.

(2) Preparation of organic EL elements 4-2 to 4-4 In the preparation of organic EL elements 4-1, organic EL elements were used except that the comparative compound (1) as the host compound was changed to the host compounds shown in Table 4. Organic EL elements 4-2 to 4-4 were produced in the same manner as in 4-1.

<< Evaluation of organic EL elements 4-1 to 4-4 >>
Evaluation similar to Example 1 was performed about each organic EL element. The evaluation results are shown in Table 4 as relative values with the organic EL element 4-1 as 100.

From the above, even when D-20 is used as the phosphorescent compound, the organic EL device using the compound having the structure represented by the general formula (I) according to the present invention as the host compound is a comparative compound ( It has been found that the luminous efficiency is equal to or higher than that in the case of using 1) and the lifetime is prolonged.

Example 5
<< Production of organic EL element >>
(1) Fabrication of organic EL element 5-1 After an ITO (indium tin oxide) film having a thickness of 150 nm was formed as an anode on a glass substrate having a size of 50 mm × 50 mm and a thickness of 0.7 mm, patterning was performed. The transparent substrate with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes, and then the transparent substrate was fixed to a substrate holder of a vacuum deposition apparatus.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.
After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing compound HAT was energized and heated, deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second, and a hole with a layer thickness of 15 nm. An injection layer was formed.

Next, Compound HT-1 was deposited in the same manner to form a hole transport layer having a layer thickness of 70 nm.
Next, the deposition rate was 0.1 nm / second so that the host compound (1), the phosphorescent compound D-20, and the phosphorescent compound D-4 were 88%, 10%, and 2% by volume, respectively. The first light emitting layer having a layer thickness of 15 nm was formed.
Next, the deposition rate is set to 0.8% so that the compound H-24 having the structure represented by the general formula (I) and the phosphorescent compound D-63 according to the present invention are 90% and 10% by volume, respectively. Co-evaporation was performed at 1 nm / second to form a second light emitting layer having a layer thickness of 20 nm.

Next, Compound HB-1 was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 5 nm. Thereafter, Compound E-1 was deposited at a deposition rate of 0.1 nm / second to form an electron transport layer having a layer thickness of 45 nm. Furthermore, after forming potassium fluoride with a film thickness of 2.0 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-light-emitting surface side of the above element was covered with a can-shaped glass cover in an atmosphere of high purity nitrogen gas with a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 5-1.
Further, when an illumination device as shown in FIGS. 5 and 6 is formed using the organic EL element 5-1, and energized, white light emission is obtained, which is represented by the general formula (I) according to the present invention. It has been found that an organic EL element using a compound having a structure as a host compound can be used as a lighting device.

Example 6
<< Production of organic EL full-color display device >>
FIG. 7 shows a schematic configuration diagram of an organic EL full-color display device.
On the glass substrate 201, after patterning at a pitch of 100 μm (see FIG. 7A) on a substrate (NH45 manufactured by NH Techno Glass Co., Ltd.) having a 100 nm ITO transparent electrode 202 formed as an anode on the glass substrate 201, A non-photosensitive polyimide partition wall 203 (width 20 μm, thickness 2.0 μm) was formed between the ITO transparent electrodes 202 by photolithography (see FIG. 7B).

A hole injection layer composition having the following composition is ejected and injected on the ITO electrode 202 between the partition walls 203 using an inkjet head (manufactured by Epson Corporation: MJ800C), irradiated with ultraviolet light for 200 seconds, 60 ° C. A hole injection layer 204 having a layer thickness of 40 nm was provided by a drying process for 10 minutes (see FIG. 7C).
On the hole injection layer 204, a blue light emitting layer composition, a green light emitting layer composition and a red light emitting layer composition having the following compositions are respectively discharged and injected using an inkjet head, and dried at 60 ° C. for 10 minutes. The

light emitting layers

205B, 205G, and 205R for each color were provided (see FIG. 7D).

(Hole injection layer composition)
HT-1: 20 parts by mass Cyclohexylbenzene: 50 parts by mass Isopropylbiphenyl: 50 parts by mass (Blue light emitting layer composition)
H-18: 0.8 parts by mass D-41: 0.04 parts by mass Cyclohexylbenzene: 50 parts by mass Isopropyl biphenyl: 50 parts by mass (green light emitting layer composition)
Host compound (1): 0.7 parts by mass D-20: 0.04 parts by mass Cyclohexylbenzene: 50 parts by mass Isopropyl biphenyl: 50 parts by mass (red light emitting layer composition)
Host compound (1): 0.7 parts by mass D-4: 0.04 parts by mass Cyclohexylbenzene: 50 parts by mass Isopropyl biphenyl: 50 parts by mass

Next, an electron transport material (Compound E-1) is deposited so as to cover each of the

light emitting layers

205B, 205G, and 205R to provide an electron transport layer (not shown) having a layer thickness of 45 nm, and further lithium fluoride is deposited. An electron injection layer (not shown) having a layer thickness of 0.5 nm was provided, Al was vapor-deposited, and a cathode 206 having a thickness of 130 nm was provided to produce an organic EL element (see FIG. 7E).
It was found that the produced organic EL elements each emitted blue, green, and red light when a voltage was applied to the electrodes, and could be used as a full-color display device.
As described above, according to the present invention, it is possible to provide an organic electroluminescence element, a lighting device, and a display device that have high luminous efficiency and excellent durability.
Moreover, the organic EL element which has the said effect can be manufactured also by a wet process.

The organic electroluminescence device of the present invention is a display device, display, home lighting, interior lighting, clock or liquid crystal backlight, signboard advertisement, traffic light, light source of optical storage medium, electrophotographic copying, which includes an organic EL device. It can be suitably used as a wide light source such as a light source of a machine, a light source of an optical communication processor, a light source of an optical sensor, and a general household appliance requiring a display device.

DESCRIPTION OF SYMBOLS 1 Display 3 Pixel 5 Scan line 6 Data line 7 Power supply line 10 Organic EL element 11 Switching transistor 12 Drive transistor 13 Capacitor 101 Organic EL element 102 in an illuminating device Glass cover 105 Cathode 106 Organic EL layer 107 Glass substrate 108 with a transparent electrode Nitrogen Gas 109 Water-absorbing agent 201 Glass substrate 202 Transparent electrode 203 Partition wall 204

Hole injection layer

205B, 205G, 205R Light emitting layer A for each color A Display unit B Control unit C Wiring unit L Light emission

Claims

An organic electroluminescence device having an organic layer including at least a light emitting layer sandwiched between an anode and a cathode,
At least 1 layer of the said organic layer contains the compound which has a structure represented by the following general formula (I), The organic electroluminescent element characterized by the above-mentioned.

(In the general formula (I), R 1 to R 6 each independently represents a hydrogen atom or an unsubstituted or substituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, amino group, Alkoxy group, aryloxy group, heterocyclic oxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group Alkylthio group, arylthio group, heterocyclic thio group, sulfonyl group, sulfinyl group, ureido group, phosphoramido group, hydroxy group, mercapto group, halogeno group, cyano group, sulfo group, carboxy group, nitro group, sulfino group, Hydrazino group, imi Group, a heteroaryl group, a silyl group or a silyloxy group. However, if the substituent represented by R 1, R 3 and R 5 are all identical, are at least one of R 2, R 4 and R 6 When at least one of R 1 , R 3 and R 5 represents a different substituent, all the substituents represented by R 2 , R 4 and R 6 may be the same.)
2. The organic electro of claim 1, wherein, in the general formula (I), one to three of R 1 to R 6 are an aryl group or a heteroaryl group which are unsubstituted or have a substituent. Luminescence element.
3. The organic electroluminescence device according to claim 1, wherein in the general formula (I), at least one of R 1 to R 6 is a heteroaryl group having a nitrogen atom.
The organic light-emitting device according to any one of claims 1 to 3, wherein the light-emitting layer contains a compound having a structure represented by the general formula (I).
An organic electroluminescent element material comprising a compound having a structure represented by the general formula (I) according to any one of claims 1 to 4.